1. Field of the Invention
The invention relates to a valve assembly and method for controlling flow of gases from an engine crankcase to an engine intake manifold.
2. Background of the Invention
Positive crankcase ventilation (PCV) valves have long been used to remove crankcases gases from the crankcase of an engine. Crankcases gases are a combination of (i) blowby gases, (i.e., combusted and non-combusted combustion chamber gases which migrate past piston rings into the crankcase), (ii) fuel, (iii) air, and (iv) oil vapor. PCV valves regulate the removal of crankcase gases from the crankcase by venting the gases into the engine intake manifold. The removal of crankcases gases from the crankcase reduces the tendency of the oil to sludgexe2x80x94a condition which is more likely to occur when blowby gases react with oil under cold engine conditions.
One known PCV valve is disclosed in U.S. Pat. No. 3,709,204. The known PCV valve shuts off the flow of gases from a crankcase to an intake manifold until the temperature of the engine has increased above a predetermined temperature. In particular, the known valve shuts off flow of the crankcase gases during cold engine starting. Another similar PCV valve system is disclosed in U.S. Pat. No. 3,263,660 that shuts off flow during cold engine starting.
The known systems, however, do not adjust flow of gases from a crankcase to an intake manifold based on an engine temperature during warm engine conditionsxe2x80x94which leads to undesirable deposition of oil in the engine intake system and exhaust system. During warm operating conditions, crankcase oil is more volatile and the crankcase gases contain a higher amount of oil particles as compared to crankcase gases during cold operating conditions. The oil in the crankcase gases flowing from the crankcase can be deposited on: (i) the intake manifold which can increase evaporative emissions, (ii) the intake valves which can degrade valve sealing during combustion, and (iii) the emission catalysts which can degrade operational performance of the catalysts leading to increased emissions.
Thus, the inventors herein have recognized that there is a need for a valve assembly and method that can reduce and/or eliminate the above-mentioned deficiencies.
The foregoing problems and disadvantages are overcome by a valve assembly and method for controlling flow of gases from an engine crankcase to an intake manifold in accordance with the present invention.
A method for controlling flow of gases through a passage between an engine crankcase and an engine intake manifold according to a first aspect of the present invention is provided. The method includes decreasing a flow of gases through the passage between the crankcase and the intake manifold when a temperature of the gases is greater than a predetermined temperature.
A valve assembly for controlling flow of gases through a passage between an engine crankcase and an engine intake manifold in accordance with a second aspect of the present invention is provided. The valve assembly includes a housing configured to be coupled with the passage. The valve assembly further includes a flow control device disposed in the housing. The device decreases a flow of the gases through the housing when a temperature of the gases is greater than a predetermined temperature.
A control system for controlling flow of gases through a passage between an engine crankcase and an engine intake manifold according to a third aspect of the present invention is provided. The system includes a temperature sensor generating a first signal indicative of a temperature of the engine. The system further includes a valve assembly having a housing and a flow control device disposed in the housing. The housing is configured to be coupled with the passage. The flow control device is configured to decrease a flow of gases through the housing responsive to a second signal. Finally, the system includes a controller operably connected to the temperature sensor and the valve assembly. The controller generates the second signal when the first signal indicates the temperature is above a predetermined temperature.
The valve assembly, control system, and method for controlling the flow of gases from an engine crankcase to an intake manifold reduces oil being deposited in the engine intake system and exhaust system during warm engine conditions. In particular, the inventive assembly and method decrease flow of gases from the crankcase to the intake manifoldxe2x80x94when a temperature within the engine is above a predetermined temperaturexe2x80x94to reduce an amount of oil inducted and deposited into the intake manifold. As a result, the amount of oil inducted into the engine cylinders and subsequently reaching a downstream emission catalyst is also reduced. Thus, degradation of the catalyst operating efficiency due to oil being deposited in the catalyst can be reduced and/or eliminated.